Android KitKat
Android KitKat brings all of Android's most innovative, most beautiful, and most useful features to more devices everywhere.
This document provides a glimpse of what's new for developers.
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Making Android for everyone
Android 4.4 is designed to run fast, smooth, and responsively on a much broader range of devices than ever before — including on millions of entry-level devices around the world that have as little as 512MB RAM.
KitKat streamlines every major component to reduce memory use and introduces new APIs and tools to help you create innovative, responsive, memory-efficient applications.
OEMs building the next generation of Android devices can take advantage of targeted recommendations and options to run Android 4.4 efficiently, even on low-memory devices. Dalvik JIT code cache tuning, kernel samepage merging (KSM), swap to zRAM, and other optimizations help manage memory. New configuration options let OEMs tune out-of-memory levels for processes, set graphics cache sizes, control memory reclaim, and more.
In Android itself, changes across the system improve memory management and reduce memory footprint. Core system processes are trimmed to use less heap, and they now more aggressively protect system memory from apps consuming large amounts of RAM. When multiple services start at once — such as when network connectivity changes — Android now launches the services serially, in small groups, to avoid peak memory demands.
For developers, Android 4.4 helps you deliver apps that are efficient and responsive on all devices. A new API, ActivityManager.isLowRamDevice(), lets you tune your app's behavior to match the device's memory configuration. You can modify or disable large-memory features as needed, depending on the use-cases you want to support on entry-level devices. Learn more about optimizing your apps for low-memory devices here.
New tools give also give you powerful insight into your app's memory use. The procstats tool details memory use over time, with run times and memory footprint for foreground apps and background services. An on-device view is also available as a new developer option. The meminfo tool is enhanced to make it easier to spot memory trends and issues, and it reveals additional memory overhead that hasn't previously been visible.
New NFC capabilities through Host Card Emulation
Android 4.4 introduces new platform support for secure NFC-based transactions through Host Card Emulation (HCE), for payments, loyalty programs, card access, transit passes, and other custom services. With HCE, any app on an Android device can emulate an NFC smart card, letting users tap to initiate transactions with an app of their choice — no provisioned secure element (SE) in the device is needed. Apps can also use a new Reader Mode to act as readers for HCE cards and other NFC-based transactions.
Apps declare the AIDs they support in their manifest files, along with a category identifier that indicates the type of support available (for example, "payments"). In cases where multiple apps support the same AID in the same category, Android displays a dialog that lets the user choose which app to use.
When the user taps to pay at a point-of-sale terminal, the system extracts the preferred AID and routes the transaction to the correct application. The app reads the transaction data and can use any local or network-based services to verify and then complete the transaction.
Android HCE requires an NFC controller to be present in the device. Support for HCE is already widely available on most NFC controllers, which offer dynamic support for both HCE and SE transactions. Android 4.4 devices that support NFC will include Tap & Pay for easy payments using HCE.
Printing framework
Android apps can now print any type of content over Wi-Fi or cloud-hosted services such as Google Cloud Print. In print-enabled apps, users can discover available printers, change paper sizes, choose specific pages to print, and print almost any kind of document, image, or file.
Android 4.4 introduces native platform support for printing, along with APIs for managing printing and adding new types of printer support. The platform provides a print manager that mediates between apps requesting printing and installed print services that handle print requests. The print manager provides shared services and a system UI for printing, giving users consistent control over printing from any app. The print manager also ensures the security of content as it's passed across processes, from an app to a print service.
You can add printing support to your apps or develop print services to support specific types of printers.
Client apps can use new APIs to add printing capabilities to their apps with minimal code changes. In most cases, you would add a print action to your Action Bar and a UI for choosing items to print. You would also implement APIs to create print jobs, query the print manager for status, and cancel jobs. This lets you print nearly any type of content, from local images and documents to network data or a view rendered to a canvas.
For broadest compatibility, Android uses PDF as its primary file format for printing. Before printing, your app needs to generate a properly paginated PDF version of your content. For convenience, the printing API provides native and WebView helper classes to let you create PDFs using standard Android drawing APIs. If your app knows how to draw the content, it can quickly create a PDF for printing.
Most devices running Android 4.4 will include Google Cloud Print pre-installed as a print service, as well as several Google apps that support printing, including Chrome, Drive, Gallery, and QuickOffice.
Storage access framework
A new storage access framework makes it simple for users to browse and open documents, images, and other files across all of their their preferred document storage providers. A standard, easy-to-use UI lets users browse files and access recents in a consistent way across apps and providers.
Box and others have integrated their services into the storage access framework, giving users easy access to their documents from apps across the system.
If you build a document provider for a cloud or local service, you can deliver it to users as part of your existing Android app. After downloading and installing the app, users will have instant access to your service from any app that participates in the framework. This can help you gain exposure and user engagement, since users will find your services more easily.
If you develop a client app that manages files or documents, you can integrate with the storage access framework just by using new CREATE_DOCUMENT or OPEN_DOCUMENT intents to open or create files — the system automatically displays the standard UI for browsing documents, including all available document providers.
You can integrate your client app one time, for all providers, without any vendor-specific code. As users add or remove providers, they’ll continue to have access to their preferred services from your app, without changes or updates needed in your code.
The storage access framework is integrated with the existing GET_CONTENT intent, so users also have access to all of their previous content and data sources from the new system UI for browsing. Apps can continue using GET_CONTENT as a way to let users import data. The storage access framework and system UI for browsing make it easier for users to find and import their data from a wider range of sources.
Most devices running Android 4.4 will include Google Drive and local storage pre-integrated as document providers, and Google apps that work with files also use the new framework.
Low-power sensors
Sensor batching
Android 4.4 introduces platform support for hardware sensor batching, a new optimization that can dramatically reduce power consumed by ongoing sensor activities.With sensor batching, Android works with the device hardware to collect and deliver sensor events efficiently in batches, rather than individually as they are detected. This lets the device's application processor remain in a low-power idle state until batches are delivered. You can request batched events from any sensor using a standard event listener, and you can control the interval at which you receive batches. You can also request immediate delivery of events between batch cycles.
Sensor batching is ideal for low-power, long-running use-cases such as fitness, location tracking, monitoring, and more. It can makes your app more efficient and it lets you track sensor events continuously — even while the screen is off and the system is asleep.
Sensor batching is currently available on Nexus 5, and we're working with our chipset partners to bring it to more devices as soon as possible.
Moves and Runtastic Pedometer are using the hardware step-detector to offer long-running, low-power services.
Step Detector and Step Counter
Android 4.4 also adds platform support for two new composite sensors — step detector and step counter — that let your app track steps when the user is walking, running, or climbing stairs. These new sensors are implemented in hardware for low power consumption.The step detector analyzes accelerometer input to recognize when the user has taken a step, then triggers an event with each step. The step counter tracks the total number of steps since the last device reboot and triggers an event with each change in the step count. Because the logic and sensor management is built into the platform and underlying hardware, you don't need to maintain your own detection algorithms in your app.
Step detector and counter sensors are available on Nexus 5, and we're working with our chipset partners to bring them to new devices as soon as possible.
SMS provider
If you develop a messaging app that uses SMS or MMS, you can now use a shared SMS provider and new APIs to manage your app's message storage and retrieval. The new SMS provider and APIs define a standardized interaction model for all apps that handle SMS or MMS messages.
Along with the new provider and APIs, Android 4.4 introduces new semantics for receiving messages and writing to the provider. When a message is received, the system routes it directly to the user's default messaging app using the new SMS_DELIVER intent. Other apps can still listen for incoming messages using the SMS_RECEIVED intent. Also, the system now allows only the default app to write message data to the provider, although other apps can read at any time. Apps that are not the user's default can still send messages — the system handles writing those messages to the provider on behalf of the app, so that users can see them in the default app.
The new provider and semantics help to improve the user's experience when multiple messaging apps are installed, and they help you to build new messaging features with fully-supported, forward-compatible APIs.
New ways to build beautiful apps
A new immersive mode lets apps use every pixel on the screen to show content and capture touch events.
Full-screen Immersive mode
Now your apps can use every pixel on the device screen to showcase your content and capture touch events. Android 4.4 adds a new full-screen immersive mode that lets you create full-bleed UIs reaching from edge to edge on phones and tablets, hiding all system UI such as the status bar and navigation bar. It's ideal for rich visual content such as photos, videos, maps, books, and games.In the new mode, the system UI stays hidden, even while users are interacting with your app or game — you can capture touch events from anywhere across the screen, even areas that would otherwise be occupied by the system bars. This gives you a great way to create a larger, richer, more immersive UI in your app or game and also reduce visual distraction.
To make sure that users always have easy, consistent access to system UI from full-screen immersive mode, Android 4.4 supports a new gesture — in immersive mode, an edge swipe from the top or bottom of the screen now reveals the system UI.
To return to immersive mode, users can touch the screen outside of the bar bounds or wait for a short period for the bars to auto-hide. For a consistent user experience, the new gesture also works with previous methods of hiding the status bar.
Transitions framework for animating scenes
Most apps structure their flows around several key UI states that expose different actions. Many apps also use animation to help users understand their progress through those states and the actions available in each. To make it easier to create high-quality animations in your app, Android 4.4 introduces a new transitions framework.The transitions framework lets you define scenes, typically view hierarchies, and transitions, which describe how to animate or transform the scenes when the user enters or exits them. You can use several predefined transition types to animate your scenes based on specific properties, such as layout bounds, or visibility. There's also an auto-transition type that automatically fades, moves, and resizes views during a scene change. In addition, you can define custom transitions that animate the properties that matter most to your app, and you can plug in your own animation styles if needed.
With the transitions framework you can also animate changes to your UI on the fly, without needing to define scenes. For example, you can make a series of changes to a view hierarchy and then have the TransitionManager automatically run a delayed transition on those changes.
Once you've set up transitions, it's straightforward to invoke them from your app. For example, you can call a single method to begin a transition, make various changes in your view hierarchy, and on the next frame animations will automatically begin that animate the changes you specified.
Apps can use new window styles to request translucent system bars.
Translucent system UI styling
To get the most impact out of your content, you can now use new window styles and themes to request translucent system UI, including both the status bar and navigation bar. To ensure the legibility of navigation bar buttons or status bar information, subtle gradients is shown behind the system bars. A typical use-case would be an app that needs to show through to a wallpaper.Enhanced notification access
Notification listener services can now see more information about incoming notifications that were constructed using the notification builder APIs. Listener services can access a notification's actions as well as new extras fields — text, icon, picture, progress, chronometer, and many others — to extract cleaner information about the notification and present the information in a different way.
Chromium WebView
Android 4.4 includes a completely new implementation of WebView that's based on Chromium. The new Chromium WebView gives you the latest in standards support, performance, and compatibility to build and display your web-based content.Chromium WebView provides broad support for HTML5, CSS3, and JavaScript. It supports most of the HTML5 features available in Chrome for Android 30. It also brings an updated version of the JavaScript Engine (V8) that delivers dramatically improved JavaScript performance.
In addition, the new Chromium WebView supports remote debugging using Chrome DevTools. For example, you can use Chrome DevTools on your development machine to inspect, debug, and analyze your WebView content live on a mobile device.
The new Chromium WebView is included on all compatible devices running Android 4.4 and higher. You can take advantage of the new WebView right away, and with minimum modifications to existing apps and content. In most cases, your content will migrate to the new implementation seamlessly. New media capabilities
Screen recording
Now it's easy to create high-quality video of your app, directly from your Android device. Android 4.4 adds support for screen recording and provides a screen recording utility that lets you start and stop recording on a device that's connected to your Android SDK environment over USB. It's a great new way to create walkthroughs and tutorials for your app, testing materials, marketing videos, and more.With the screen recording utility, you can capture video of your device screen contents and store the video as an MP4 file on the device. You can record at any device-supported resolution and bitrate you want, and the output retains the aspect ratio of the display. By default, the utility selects a resolution equal or close to the device's display resolution in the current orientation. When you are done recording, you can share the video directly from your device or pull the MP4 file to your host computer for post-production.
If your app plays video or other protected content that you don’t want to be captured by the screen recorder, you can use SurfaceView.setSecure() to mark the content as secure.
You can access screen recording through the adb tool included in the Android SDK, using the command adb shell screenrecord. You can also launch it through the DDMS panel in Android Studio.
Resolution switching through adaptive playback
Android 4.4 brings formal support for adaptive playback into the Android media framework. Adaptive playback is an optional feature of video decoders for MPEG-DASH and other formats that enables seamless change in resolution during playback. The client can start to feed the decoder input video frames of a new resolution and the resolution of the output buffers change automatically, and without a significant gap.Resolution switching in Android 4.4 lets media apps offer a significantly better streaming video experience. Apps can check for adaptive playback support at runtime using existing APIs and implement resolution-switching using new APIs introduced in Android 4.4.
Common Encryption for DASH
Android now supports the Common Encryption (CENC) for MPEG-DASH, providing a standard, multiplatform DRM scheme for managing protecting content. Apps can take advantage of CENC through Android's modular DRM framework and platform APIs for supporting DASH.HTTP Live Streaming
Android 4.4 updates the platform's HTTP Live Streaming (HLS) support to a superset of version 7 of the HLS specification (version 4 of the protocol). See the IETF draft for details.Audio Tunneling to DSP
For high-performance, lower-power audio playback, Android 4.4 adds platform support for audio tunneling to a digital signal processor (DSP) in the device chipset. With tunneling, audio decoding and output effects are off-loaded to the DSP, waking the application processor less often and using less battery.Audio tunneling can dramatically improve battery life for use-cases such as listening to music over a headset with the screen off. For example, with audio tunneling, Nexus 5 offers a total off-network audio playback time of up to 60 hours, an increase of over 50% over non-tunneled audio.
Media applications can take advantage of audio tunneling on supported devices without needing to modify code. The system applies tunneling to optimize audio playback whenever it's available on the device.
Visualization of how the LoudnessEnhancer effect can make speech content more audible.
Audio monitoring
Apps can use new monitoring tools in the Visualizer effect to get updates on the peak and RMS levels of any currently playing audio on the device. For example, you could use this creatively in music visualizers or to implement playback metering in a media player.Loudness enhancer
Media playback applications can increase the loudness of spoken content by using the new LoudnessEnhancer effect, which acts as compressor with time constants that are specifically tuned for speech.Audio timestamps for improved AV sync
The audio framework can now report presentation timestamps from the audio output HAL to applications, for better audio-video synchronization. Audio timestamps let your app determine when a specific audio frame will be (or was) presented off-device to the user; you can use the timestamp information to more accurately synchronize audio with video frames.Wi-Fi CERTIFIED Miracast™
Android 4.4 devices can now be certified to the Wi-Fi Alliance Wi-Fi Display Specification as Miracast compatible. To help with testing, a new Wireless Display developer option exposes advanced configuration controls and settings for Wireless Display certification. You can access the option at Settings > Developer options > Wireless display certification. Nexus 5 is a Miracast certified wireless display device.RenderScript Compute
Performance benchmarks for Android 4.4 relative to Android 4.3, run on the same devices (Nexus 7, Nexus 10).
Ongoing performance improvements
When your apps use RenderScript, they'll benefit from ongoing performance tuning in the RenderScript runtime itself, without the need for recompilation. The chart at right shows performance gains in Android 4.4 on two popular chipsets.GPU acceleration
Any app using RenderScript on a supported device benefits from GPU acceleration, without code changes or recompiling. Since the Nexus 10 first debuted RenderScript GPU acceleration, various other hardware partners have added support.Now with Android 4.4, GPU acceleration is available on the Nexus 5, as well as the Nexus 4, Nexus 7 (2013), and Nexus 10, and we're working with our partners to bring it to more devices as soon as possible.
RenderScript in the Android NDK
Now you can take advantage of RenderScript directly from your native code. A new C++ API in the Android Native Development Kit (NDK) lets you access the same RenderScript functionality available through the framework APIs, including script intrinsics, custom kernels, and more.If you have large, performance-intensive tasks to handle in native code, you can perform those tasks using RenderScript and integrate them with your native code. RenderScript offers great performance across a wide range of devices, with automatic support for multi-core CPUs, GPUs, and other processors.
When you build an app that uses the RenderScript through the NDK, you can distribute it to any device running Android 2.2 or or higher, just like with the RenderScript support library available for framework APIs.
Graphics
GLES2.0 SurfaceFlinger
Android 4.4 upgrades its SurfaceFlinger from OpenGL ES 1.0 to OpenGL ES 2.0.New Hardware Composer support for virtual displays
The latest version of Android Hardware Composer, HWComposer 1.3, supports hardware composition of one virtual display in addition to the primary, external (e.g. HDMI) display, and has improved OpenGL ES interoperability.New Types of Connectivity
New Bluetooth profiles
Android 4.4 support for two new Bluetooth profiles to let apps support a broader range of low-power and media interactions. Bluetooth HID over GATT (HOGP) gives apps a low-latency link with low-power peripheral devices such as mice, joysticks, and keyboards. Bluetooth MAP lets your apps exchange messages with a nearby device, for example an automotive terminal for handsfree use or another mobile device. As an extension to Bluetooth AVRCP 1.3, users can now set absolute volume on the system from their Bluetooth devices.Platform support for HOGP, MAP, and AVRCP is built on the Bluedroid Bluetooth stack introduced by Google and Broadcom in Android 4.2. Support is available right away on Nexus devices and other Android-compatible devices that offer compatible Bluetooth capabilities.
IR Blasters
Android 4.4 introduces platform support for built-in IR blasters, along with a new API and system service that let you create apps to take advantage them.Using the new API, you can build apps that let users remotely control nearby TVs, tuners, switches, and other electronic devices. The API lets your app check whether the phone or tablet has an infrared emitter, query it's carrier frequencies, and then send infrared signals.
Because the API is standard across Android devices running Android 4.4 or higher, your app can support the broadest possible range of vendors without writing custom integration code.
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